Wow, it sounds like you have your hands full. I am going to say some things that I expect you will keep in context as being largely hypothetical. I have not studied MCS nor am I trained in chemical sciences.
The only hypothesis that I have seen about the pathophysiology of MCS is the one proposed by Dr. Pall. It does seem that many benefit from his treatment approach of largely using antioxidant compounds to suppress peroxynitrite, superoxide, etc.. I think this suggests there may be some validity to his hypothesis. In my opinion, though, some of the supplements he recommends for purposes of downregulating this NO/ONOO cycle are contraindicated. More consequentially though, this treatment is not likely going to lead to restoration of the underlying pathophysiology. This is similar to Rich's idea's about using methyl donors in ME/CFS. He correctly identified the problem of a redox imbalance with may symptoms certainly created by limited availability reduced glutathione, but I don't think he ever viewed this as a counter-regulatory response.
Like Pall I similarly believe the suppression of these free radicals is fundamental to solving ME/CFS, but I suspect, that many would benefit from treating what I believe to be the source of this problem: the dysbiosis and epithelial dysfunction in the GIT that is maintained by these organisms. Using antioxidants for symptom suppression is likely advantageous and can contribute to recovery; I benefited very dramatically from lipoic acid, which acts at a key point of the metabolism where our energy biosynthesis is undermined. But, I think the restoration of the intestinal epithelial barrier, specifically with the provision of butyrate offers the greatest potential to suppress oxidative and nitrosative stress and correct the aforementioned problems. This is where the battle against these free radicals has to be fought. This is where nitrogen metabolism is deranged, this is where losses in the electron transport chain and glycolysis, etc. take place, these processes are metabolically fundamental.
What I do know about MCS and food sensitivities is that they are frequently, if not nearly universally, co-occuring. I believe this relates to the dysbiotic conditions, particularly at the intestinal epithelium and the explanations but it is important to note that the food sensitivities are not singularly explained.
One thing that happens in ME/CFS is a degradation of the ability to chemically modify our foods. Some food sensitivities clearly relate to the lack of human and bacterial enzymatic capacity to degrade these compounds. In fact, I think there is a parallel and intentional response in loss of energy and secretion of pancreatic enzymes that occurs. Said another way, when we loose the microbes that create enzymes that participate in the breakdown of macronutrients and indigestible or resistant polysaccharides, there is a similar inhibition of our own human digestive enzymatic capacity. We commonly see this when someone is afflicted with severe ME/CFS and starts to develop severe food intolerance, weight loss, fat malabsorption, and obvious pancreatic insufficiency. Think about what this achieves functionally, it suppresses the immune response, which is mediated by many of the compounds and micronutrients contained in our foods. Availability of zinc, fat soluble vitamins A, E, D, & K. This is of course comes with adverse immune consequences, including the creation of antibodies, but I would argue that the higher priority, in the setting of a compromised intestinal epithelium barrier involves suppressing the immune/inflammatory response. As I have studied ME/CFS, I see level after level of ways this has done and the provision of butyrate has a special ability to start to reverse many of these processes unlike anything else I have found.
But there is clearly more to the food sensitivities than poor enzymatic degradation of macronutrients. You can supplement with prebiotics and probiotics and enhance your ability to breakdown these foods, like nurturing organisms with robust amylase enzyme capability to chemically degrade carbohydrates, for example, but this isn't going to correct the energy deficits. I believe many of the food intolerances and the odors that precipitate MCS symptoms relate to particular categories of aroma compounds. What has not been identified, to my knowledge, is that there are organisms that maintain the intestinal epithelium that play specific roles in degrading these compounds. Accordingly, when the ecological community at the intestinal epithelium becomes deranged we simultaneously lose our ability to generate normal energy levels, we stimulate an enormous extra-intestinal inflammatory immune response, we suffer a degraded capability metabolize compounds via the CYP-450 liver enzymes, and very specific compounds utilized by specific organism are no longer efficiently utilized and prove to have toxic consequences. At a cellular level I believe the epithelial dysfunction allows for these chemicals to initiate changes in Nitric oxide and the NOS enzymes that induce these adverse symptoms in the nose/gut/brain that teach us to avoid the offending compounds. NO, iNOS, eNOS play roles critical in maintaining the homeostasis at the intestinal epithelium and also the olfactory cells (in the nose) which transmit odors to the brain.
So if nitric oxide plays an indispensable role in establishing how your brain responds to odors, I think it is reasonable that dysregulation of NO/ONOO contributes to a superphysiological response to odors, but we need to fix the root problem, which is easier said than done.
Take a look at the link and you will see many of the offending compounds. As alluded to above, there are organisms at the surface of the large intestine that have special affinity for some of these compounds. These are highly specialized organisms that can contribute to the metabolism of these compounds while simultaneously contributing to the maintenance of the intestinal epithelium. In fact, I find that these organisms are concentrated at the mucuosal barrier and not in the lumen.
You will see that your old adversary, cut grass, is on this list: cis-3-hexen-1-ol. You seem to have particular sensitivity to aromatic alcohols and probably aldehydes. The better we are able to categorize offensive compounds, perhaps the more likely we are able to find a solution that matches this. You see, there is a reason I have been talking about these chemical compounds for so long. Foods with the highest content of these compounds which create adverse reactions commonly and often proportionately contain resistant polysaccharides,which stimulate the growth of organisms that are most suited to the microbial metabolism of these chemicals. I hope this is not too theoretical for you, but is see a potential role for specific resistant polysaccharides.
Let me know what you think of this list:
http://en.wikipedia.org/wiki/Aroma_compound